Future Darcy Lecturer

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2017 Darcy Lecture

Kamini Singha, Ph.D., is a professor in the Department of Geology and
Geological Engineering and the associate director of the Hydrologic
Science and Engineering Program at the Colorado School of Mines. She
worked at the U.S. Geological Survey Branch of Geophysics from 1997 to 2000, and was a
member of the faculty at The Pennsylvania State University from 2005 to
2012. She earned her B.S. in geophysics from the University of
Connecticut in 1999 and her Ph.D. in hydrogeology from Stanford
University in 2005.

Lecture descriptions

A Tale of Two Porosities: Exploring Why Contaminant Transport Doesn’t Always Behave the Way It Should

Transport
through preferential flowpaths is important in a broad range of
scientific disciplines. In hydrology, the ability to quantify subsurface
transport is an issue of paramount importance due to problems
associated with groundwater contamination. Observational challenges and
complexity of hydrogeological systems lead to severe prediction
challenges with standard measurement techniques. One important example
of a prediction challenge is “anomalous” solute-transport behavior,
defined by characteristics such as concentration rebound, long
breakthrough tailing, and poor pump-and-treat efficiency.

These
phenomena have been observed at research and aquifer-remediation sites
in diverse geologic settings, and are not predicted by classical theory.
Numerous conceptual models have been developed to explain anomalous
transport, such as the presence of two distinct populations of pores — one
where solutes are highly mobile and another where they are not — but
verification and inference of controlling parameters in these models in
situ remains problematic, and often estimated based on data fitting
alone. Recent tests using simple electric geophysical methods directly
measure the process of mobile-immobile mass transfer and allow
estimation of parameters controlling anomalous transport.

This
lecture presents a rock-physics framework, an experimental methodology,
and analytical expressions that can be used to determine parameters
controlling anomalous solute transport behavior from colocated
hydrologic and electrical geophysical measurements in a series of
settings, including groundwater and surface water/groundwater systems.
The long-term goals of this work are to contribute toward improving the
predictive capabilities of numerical models and enhancing the fidelity
of long-term groundwater monitoring frameworks.

The Critical Role of Water in Critical Zone Science: An Exploration of Water Fluxes in the Earth’s Permeable Skin

Earth’s
“critical zone” — the zone of the planet from treetops to base of
groundwater — is critical because it is a sensitive region, open to
impacts from human activities, while providing water necessary for human
consumption and food production. Quantifying water movement in the
subsurface is critical to predicting how water-driven critical zone
processes respond to changes in climate and human perturbation of the
natural system. While shallow soils and aboveground parts of the
critical zone can be easy to instrument and explore, the deeper parts of
the critical zone — through the soils and into rock — are harder to access,
leaving many open questions about the role of water in this
environment.

This presentation opens the black box in the
subsurface and sheds light on a few key subsurface processes that control
water movement and availability: linkages between changes in
evapotranspiration and subsurface water stores, water movement in three dimensions
over large areas, and potential control of slope aspect on subsurface
permeability. Geophysical tools are central to the quantitative study of
these problems in the deeper subsurface where we don’t have easy access
for observation.

Continuing education points

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with continuing education requirements may recognize the Darcy Lecture
for credit; please check with your state/local licensing board or
regulatory body.

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